The present invention relates to a semiconductor device, and more particulary to a reverse blocking type switching device which can be rapidly turned off without containing any lifetime killer, (for example, a gate turnoff thyristor, an electrostatic induction type thyristor, and others).
A gate turn-off thyristor (hereinafter simply referred to as "GTO") is classified into two groups. In one of the groups, the emitter junction on the anode side is not short-circuited by an anode electrode, as shown in FIGS. 1 and 4 of a Japanese Patent Unexamined Publication No. 57-178369. In the other group, the emitter junction on the anode side is shorted by an anode electrode, as shown in FIG. 2 of the above Japanese Patent Application. The former group has a reverse blocking function. In this group, however, a lifetime killer is added to the whole of a semiconductor substrate to enhance the turn-off speed, and hence there arises a problem that a leak current in a blocking state becomes large. The latter group can perform a high-speed operation without containing any lifetime killer, and hence the leak current in the blocking state is small. However, the latter group does not have the reverse blocking function. That is, each of the two groups has both merits and demerits. The same is true of an electrostatic induction type thyristor.